Sheet wrapping material containing nitro-phenol compound



nited States Patent 0 SHEET WRAPPING MATERIAL CONTAINING NITRO-PHENOL COMPOUND Aaron Wachter and Robert J. Moore, Oakland, Calif.,

assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application February 25, 1950, Serial No. 146,386

10 Claims. (Ch ll-4.5)

This invention relates to corrosion inhibition. More specifically, this invention relates to novel'vapor-phase inhibitors, particularly compositions containing such inhibitors, and techniques of utilization thereof.

A vapor-phase corrosion inhibitor is a material, preferably solid at room temperature, the vapors from which will inhibit corrosion, particularly oxidative corrosion, of metals, especially those metals normally corroded or oxidized by the presence of water vapor in air. When using vapor-phase inhibitors'the inhibitor crystals (or other condensed forms) are merely disposed in the vicinity of the metal to be protected, and the extremely low concentrations of vapors from the inhibitor will give protection from corrosion by any moisture-containing air also in the vicinity of the metal. Thus, there need be no special precautions taken either to exclude moist air from the metal surface or (as, for example, in the case of a rust-preventive oil) to insure complete coverage of the metal surface by the inhibitor.

The problems involved in atmospheric corrosion of metals, especially ferruginous metals, by atmospheres containing water vapor and oxygen, e. g., moist or humid air, are well known to manufacturers, handlers, and users of such metals. Prior to the discovery of vapor-phase corrosion inhibitors, the only methods for combating such corrosion were either to separate the metals from the corrosive atmosphere with a coating, such as a paint, oil or grease, orto extract one or more of the corrosiveelemen'ts from the atmosphere, such as by the use of a dehydrating agent, to dry the air. These methods are, in general, either too time-consuming or too inefiective to be completely satisfactory. However, under proper circumstances, as described more fully below, the use of vaporphase corrosion inhibitors provides a simple and very satisfactory solution to the problems of corrosion.

It is, therefore, an object of this invention to provide novel and effective vapor-phase corrosion inhibitors and compositions. It is another object of the present invention to provide new methods utilizing, and combinations including, such inhibitors and compositions. objects will be obvious from the description hereinafter.

It has now been found that nitrophenols and metal salts thereof, especially the base metal salts, are effective vapor-phase corrosion inhibitors. More particularly, it has been found that the nitrophenols having a molecular weight of less than about 350 and preferably less than about 250, and the salts of these phenols are especially effective. The preferred compounds are those in which a nitro group is attached to an aromatic ring in position ortho to a hydroxy group.

The generic term nitrophenols is intended to include those compounds which have at least one benzene ring and at least one hydroxy and at least one nitro group attached to said ring. In general, the hydrocarbon nucleus, which may be either a rnonocyclic aromatic or fused ring aromatic system and may contain other hydrocarbyl substituents as a part thereof, will be substituted only with nitro and hydroxy groups. It is quite clear, however,

Additional "ice that the nitro-hydroxy-aromatic compounds may also contain other relatively stable substituents, such as alkoxy, keto, and ester groups, and the like, so long as the groups do not react with the nitro or hydroxy groups, or change the essential characteristics imparted to the compound by the nitro and hydroxy groups.

The term base metal, as used herein, is intended to include not only the mono-valent alkali metals, such as lithium, sodium, potassium, etc., but also the divalent alkaline earth metals, such as calcium and magnesium. As indicated above, the base metal salts are preferred; however, other metal salts, such as the Zinc, aluminum, iron, etc., salts are also eifective.

Examples of various nitrophenols which are suitable vapor-phase corrosion inhibitors are otho, meta and para nitrophenol, 2,4- and 2,6-dinitrophenol; 2-nitro-4, 6-dimethylphenol; 2-methyl-4-tertiary amyl-6-nitrophenol; 2,6 dinitro 4 isooctylphenol; 4 nitroresorcinol-1,3; 3- nitro-4-hydroxy-benzyl alcohol; alpha-nitro-beta-naphthol; etc. Likewise, the sodium, potassium, calcium and other base metal salts of the above compounds,-such as, for example, sodium ortho-nitrophenolate, may be eifec tively used as vapor-phase corrosion inhibitors.

The metals which are protectedby the inhibitors of this invention are those metals which are normally corroded by water vapor in air. included in such metals are the ferrous metals such as Armco iron, plain carbon steels of high, low and medium carbon content, and cast irons; ferruginous alloys, including high alloy content steels, ferritic and austenitic steels, and the like. Also protected by the inhibitors of this invention are various non-ferrous metals such as copper, aluminum, magnesium, etc., and the non-ferrous alloys of such. Thus, in general, those metals, the oxides of which are spontaneously formed under ordinary temperature and pressure conditions, are protected according to this invention. Protection also has been achieved for couples of dissimilar metals, such as couples of steel with copper, aluminum, nickel and chromium, and alloys of these metals.

Various techniques are effective in the utilization of the present materials as vapor-phase corrosion inhibitors. For example, within any enclosing means or container, corrosion of metal surfaces by moisture is preventedby the presence, in the enclosed gaseous atmosphere, of very small amounts of the above compounds. These compounds may be originally introduced into the enclosure as a solid, liquid, or vapor, in a solution, or as an emulsion or a dispersion, etc., just so long as the inhibitor vapors may diffuse throughout the atmosphere in contact with the metal Within the enclosure. Thus, a metal article may be placed in a container together with the inhibitors as crystals or as a powder; or there may be introduced into the enclosure or container a solid material, preferably an absorbent or fibrous material, coated or impregnated with the present inhibitors.

In a preferred embodiment of the instant invention, the present vapor-phase inhibitors are coated upon, or impregnated within, a solid sheet packaging or wrapping material, such as paper, cardboard, cloth or various textile materials, metal foil, plastic films or sheets, and the like, which may be used for packaging metallic objects. Laminates of the above materials, only parts of which are impregnated with, or otherwise contain, the above inhibitors, are also useful. In the case of the latter type of packaging material, the metal is preferably wrapped so that the inhibitor-containing side of the wrappin g is toward the metal. The inhibitors may be impregnated in the wrappings by various means, such as, e. g., dissolving them (the inhibitors) in a relatively volatile solvent therefor, such as acetone, alcohol, or water soaking the wrapping in the resulting solution and allowing the solvent to evaporate. Or the salts may be impregnated in the carrier by successive treatments with solutions of reactants for forming the salts within the carrier. The inhibitors may also be coated on the various materials, such as by means of a suspension in an adhesive starch or the like.

After providing the containers with the inhibitors in any of the above or equivalent forms, the containers may then be closed or sealed. The resultant container or package need not be completely airtight, but only has to be closed to the extent that a corrosion-inhibiting concentration of vapors is retained or maintained within the package.

In cases wherein free circulation of air is prevented around metal articles in storage, the inhibitors are also effectively utilized by introducing them as vapors around the metal articles. Corrosion by circulation of air over metal surfaces can be prevented by partially or substantially saturating the introduced air with vapors of the inhibitors. Metal parts can be effectively corrosionproofed by coating them with the inhibitors by depositing the latter from a solution or a dispersion, or from heated vapors contacting a cooler metal, or by incorporating the inhibitors in relatively non-volatile coating materials which remain on the metal.

The metal walls or moving parts within machinery or instruments may be prevented from corroding either by enclosing the inhibitors, or by otherwise making the inhibitors available, within vapor spaces therein.

Aerosols are also effective for distributing the inhibitors. In such a case, the inhibitor is dissolved in a liquefied normally-gaseous solvent which is under sufficient pressure in a vessel to maintain the solvent in a liquid state. The solution of the inhibitor thus prepared is released through a restricted orifice in the vessel, thereby distributing the inhibitor in a state of minute subdivision.

A particularly advantageous characteristic of the vaporphase corrosion inhibitors stems from the facts that the inhibitors are effective in extremely low concentrations in the vapor phase and that, under ordinary atmospheric conditions of temperature and pressure, they are relatively stable solids having rather low volatilities. Thus, the condensed inhibitor acts as a reservoir to replace inhibitor vapors which escape from the enclosure, are used up, or are otherwise removed from the corrosion-inhibiting atmospheres.

From the above, it is obvious that the duration, but not the degree, of corrosion protection is dependent upon the amounts of inhibitors used in accordance with this invention, with the obvious reservation that the initial supply must be suflicient to build up a corrosion-inhibiting concentration, but minute amounts of inhibitor will usually satisfy this latter requirement. Consequently, the amount to be used in any particular application will depend upon such things as the length of time for which protection is required and upon the rate at which the inhibitor is allowed to escape, and will vary with the individual applications. In general, satisfactory results are attained when the inhibitor is present in an amount of between about 0.01 gm. and about gm. (for average conditions, about 1 to 4 gm.) per cubic foot of enclosed vapor space. In the case of wrapping, or packaging materials, between about 0.01 gm. and about 5 gm. of inhibitor per square foot of sheet material is generally satisfactory. It should be obvious, however, that extreme conditions may require much greater or much smaller amounts than those stated. It may often be advantageous to use a combination of two or more inhibitors.

Although not necessary for the complete understanding and successful practice of this invention, the following examples are presented to show the surprising results which may be attained by the use of the present vaporphase corrosion inhibitors. It is emphasized that these examples are merely illustrative, and the invention should 1n no way be construed as limited thereby.

- o-Nitrophenol.

Example I Steel pieces of low carbon content, inch by 2 inches and about ,6 inch thick, were thoroughly cleaned of normal sur-face dirt and contamination so as to present a freshly exposed surface of the metal. The metal was washed with acetone and thoroughly dried in a vacuum dessicator. The steel pieces were then weighed and suspended from a glass hook attached to the inner hollow of a glass stopper of a ml. wide-mouth bottle. Onehalf gram of the compound to be tested as a vapor-phase corrosion-inhibitor and 0.5 milliliter (ml.) of distilled water were placed in the bottom of each bottle. The steel pieces were not in contact with these materials. The test-bottles with the specified contents were then maintained at a temperature of F. for seven days, after which the steel specimens were removed, washed with acetone and dried in a vacuum desiccator. The weight changes were then measured. The following results were obtained:

Vapor-phase tests were carried out in the same manner as described in Example I except that the steel specimens were not weighed and three different temperatures were employed. The following results were obtained:

Inhibitor Temperature fggg fi gf gg g Room (about 20 0.)..

bright.

97% to 95% protection from corrosion, only 35% black specks, no brown rust.

Example III Vapor-phase tests were carried out in the same manner as described in Example I except that a temperature of 86 F. (instead of 150 F.) was employed, and the specimens consisted of polished boiler plate steel.

In cases where elevated or excessively high temperatures are encountered during vapor phase-corrosion-inhibition over prolonged periods of time, it is advantageous to incorporate with the nitro-aryl-hydroxyl compound(s) a relatively weak alkaline organic or inorganic material, of an order of basicity which neutralizes acids stronger than the acidity of the nitro-aryl-hydroxyl compounds. This neutralizes minor amounts of nitric acid which may der d velop from partial hydrolysis of the nitro-aryI-lrydroxyl compoundts) in contact with water.

Example I V Vapor p'hase tests were carried out in tlie same manner as in Example I at a temperature of 150 F. The following results were obtained:

- elg ime Inhibitor in Mum Days Appearance of Metal grams None 102.2 7 100%tcovered with brown rus o-Nitrophenol (0.5 gm)... 0.2 7 No brow-n rusting; only about 3% to of area had scattered black specks.

Do 0. 9 14 Only about of area had scattered black specks.

D0 1. 4 21 only about of area had o-Nitrophenol (0.4 gr.) 0.1 7 No rusting; retained bright plus sodium bicarbosheen. nate (0.1 gr.).

Do 0.1 14 No brown rusting; only about 1% of scattered specks of stain.

Do 0.0 21 No brown rusting; only about 2% of scattered specks of black stain.

Example V Vapor-phase tests were carried out in substantially the same manner as described in Example I except that weight changes of the steel pieces were not measured, and the results of the tests were evaluated by visual inspection and by assigning numbers indicating their relative rating with respect to each others evident surface corrosion. It was found that meta-nitrophenol had a rating of 3 as compared with a rating of 2 for ortho-nitrophenol, while the control was demonstrated to have a rating of 46, the small rating numbers indicating substantially perfect protection from corrosion and the large rating number indicating an appearance of marked corrosion.

Example VI A carbon steel specimen, 2 inches by /2 inch by inch, was suspended in an inverted test tube lined with a single thickness of paper impregnated with the compound to be tested as a vapor-phase inhibitor. The compound was present at a concentration of 1 gram per square foot of paper. The open end of the test tube was partially closed by a cork having a inch hole therein. The test tube was suspended under a glass bell jar set in a shallow pan of water. The air in the bell jar and the water in the pan were continuously replaced. The water was heated to maintain the air temperature at about 104 F. The relative humidity of the air was maintained at between 92 and 100%. After 14 days, the following results were noted:

1 Average of 2 or more tests.

Example VII Pairs of polished mild steel strips, x 3 x 5 inches were separated 1% inches by Bakelite spacers and wrapped loosely in 6 x 7 inch rectangles of 60# kraft paper impregnated with 1.15 grams per square foot of the sodium salt of o-nitrophenol. The wrapped specimens were placed in envelopes made of 25-25-25 kraft-asphaltkraft paper, stapled shut, and sealed with wax. Other specimens were treated in a like manner, except that the 60# kraft paper wrap contained no inhibitor. The envelopes were placed on an outdoor rack, and observations as to corrosion protection were made from time to time. After six months the controls specimens had about 1% of their surface rusted, and after 1 year, nearly 10% was rusted. However, the specimens wrapped in the inhibitor impregnated papers were completely free from rust, even afterl year.

Example VIII In order to show the value of the present vapor-phase corrosion inhibitors for protecting empty steel drums, 3- gallon black iron drums were exposed to conditions under which the temperature was raised to F. and back to room temperature twice daily. 1.85 grams of water were placed in each of two drums, and 82 milligrams of onitrophenol crystals were placed in one of the drums. After 34 days the drum containing the nitrophenol was substantially free from rust, whereas the other drum was heavily rusted.

Essentially the same comparative results were obtained when closed drums with and without o-nitrophenol were exposed to atmospheric conditions out of doors for two Weeks.

Example IX In additional tests carried out in the same manner as in Example I except that only 0.1 gram of the inhibitor was used, the following results were obtained:

pending application Serial No. 690,335 filed August 13, 1946, now abandoned.

We claim as our invention:

1. A corrosion-inhibiting wrapping material comprising a substantially solid inactive sheet wrapping material having associated therewith in the solid state a compound of the group consisting of nitrophenols and base metal salts thereof, said nitrophenol having a molecular weight of less than about 350 and containing no groups other than nitro, hydroxy and hydrocarbyl groups.

2. A corrosion-inhibiting wrapping material comprising paper having associated therewith sodium orthonitrophenolate.

3. A substantially solid inactive fibrous wrapping material and, physically associated therewith in the solid state, a base metal salt of an unsubstituted nitrophenol.

4. A substantially solid inactive sheet wrapping material and, physically associated therewith in the solid state, sodium ortho-nitrophenolate.

5. A corrosion-inhibiting wrapping material comprising paper having associated therewith an alkali metal salt of ortho-nitrophenol.

6. A corrosion-inhibiting wrapping material comprising paper having associated therewith a base metal salt of ortho-nitrophenol.

7. A corrosion-inhibiting wrapping material comprising paper having associated therewith a metal salt of a nitrophenol, said nitrophenol having a molecular weight of less than about 350 and containing no groups other than nitro, hydroxy and hydrocarbyl groups.

8. A corrosion-inhibiting wrapping material comprising paper having associated therewith a sodium salt of an unsubstituted nitrophenol.

9. A corrosion-inhibiting wrapping material comprising paper having associated therewith the sodium salt of a nitrophenol, said nitrophenol having a molecular weight of less than about 250 and containing no groups other than nitro, hydroxy and hydrocarbyl groups.

10. A corrosion-inhibiting wrapping material comprising paper having associated therewith the sodium salt of a nitrophenol, said nitrophenol having a molecular weight of less than about 350 and containing no groups other than nitro, hydroxy and hydrocarbyl.

References Cited in the file of this patent UNITED STATES PATENTS 1,847,711 Calcott Mar. 1, 1932 2,304,950 Parker Dec. 15, 1942 2,330,524 Shields Sept. 28, 1943 

1. A CORROSION-INHIBITING WRAPPING MATERIAL COMPRISING A SUBSTANTIALLY SOLID INACTIVE SHEET WRAPPING MATERIAL HAVING ASSOCIATED THEREWITH IN THE SOLID STATE A COMPOUND OF THE GROUP CONSISTING OF NITROPHENOLS AND BASE METAL SALTS THEREOF, SAID NITROPHENOL HAVING A MOLECULAR WEIGHT OF LESS THAN ABOUT 350 AND CONTAINING NO GROUPS OTHER THAN NITRO, HYDROXY AND HYDROCARBYL GROUPS. 